Sodium bicarbonate containing toothpaste

ABSTRACT

A toothpaste containing at least 60% sodium bicarbonate particles as the sole abrasive, at least 30% of the sodium bicarbonate having particle sizes of less than 25 microns. Humectants, thickening agents, fluoridating agents, flavors, sweeteners and other conventional adjuvants may also be included in the toothpaste.

TECHNICAL FIELD

This invention relates to a sodium bicarbonate containing toothpaste.More particularly, this invention relates to a toothpaste containingsodium bicarbonate particles as the sole abrasive agent therein.

BACKGROUND OF THE INVENTION

Many different dentifrice compositions are known for cleaning,whitening, and preserving the teeth. Of these known dentifrices, manyinclude high contents of water-insoluble abrasives which aid in removingplaque and retarding stain build-up on the teeth. However, since theultimate goal of any oral hygiene regimen is preservation of the teeth,it is widely accepted that dentifrice compositions should include theleast abrasive material necessary to remove plaque and stain.

The use of sodium bicarbonate as an abrasive in dentifrices haspreviously been proposed. While sodium bicarbonate has been described inthe literature as an ingredient of both tooth powders (see, for example,Danner U.S. Pat. No. 1,082,681; Crowther U.S. Pat. No. 2,024,146;Cabardo U.S. Pat. No. 4,276,287; and Winston et al U.S. applicationSerial No. 628,855 filed July 9, 1984, owned by the assignee of thisinvention) and toothpastes (see, for example, Januszewski et al U.S.Pat. No. 3,935,304; and Delaney et al U.S. Pat. Nos. 3,935,305;3,937,321; 3,937,803; 3,937,804; 3,943,240; and 4,160,022), prior tothis date it has met with limited commercial success.

Tooth powders generally contain only abrasives, flavors, sweeteners, andsurfactants. On the other hand, toothpastes generally contain, inaddition to the abrasive material, humectants, thickeners and water, aswell as surfactants, flavors, and sweeteners. Both forms of dentrificemay also contain additional ingredients for special functional oresthetic reasons, for example, fluoridating or coloring agents. In viewof the distinct nature of tooth powder and toothpaste formulations and,particularly, the presence of humectants, thickeners and water intoothpastes but not tooth powders, an abrasive which is suitable for usein a tooth powder may not be suitable for use in a toothpaste and,conversely, an abrasive which is suitable in a toothpaste may not besuitable in a tooth powder.

In general, sodium bicarbonate is a desirable abrasive for dentifricecompositions because it is low in abrasion and imparts an exceptionallyclean, fresh feel to the mouth. Sodium bicarbonate particles arerelatively soft as compared to most conventional abrasive materials usedin dentifrice compositions. Thus, the American Dental Association hasrecommended that if only a slight degree of abrasion is necessary tokeep from staining, baking soda is usually a satisfactory abrasive.Accepted Dental Therapeutics, pp.340-41 (38th Ed., 1979).

Heretofore, low abrasivity has been associated with poor stain removalproperties. Secondary abrasives have, therefore, frequently beenincorporated in sodium bicarbonate containing toothpaste formulations toenhance their stain removal properties. See, for example, the aforesaidDelaney et al patents, which disclose incorporating secondary, insolubleabrasives such as silica, chalk, alumina, zirconium silicate, or aluminosilicates in amounts of 5-25%, or more, of the toothpaste formulationsdescribed therein. Similarly, Januszewski et al discloses a sodiumbicarbonate based toothpaste additionally comprising from 0.1 to 5.0%titanium dioxide to enhance the polishing ability of the formulation.

The need for a secondary abrasive to improve the polishing ability of asodium bicarbonate based dentifrice may be obviated by increasing thelevel of sodium bicarbonate in the formulation. This can be effective ina tooth powder, where there is essentially no practical limit to thelevel of sodium bicarbonate which can be incorporated into the product.However, high levels of conventional bicarbonate abrasives in toothpasteformulations impart excessively high viscosities, and prevent mixingduring manufacture. Additionally, the dispensibility of suchcompositions is unacceptable. At the maximum possible levels (about60-65%) at which conventional bicarbonate abrasives can be utilized intoothpastes, while still maintaining an acceptable consistency, thepolishing ability of the formulation is insufficient due to the mildabrasivity of this material. Thus, previous attempts to achieveacceptable cleaning power in a toothpaste formulation by incorporatingtherein high levels of sodium bicarbonate as the sole abrasive have beenunsatisfactory.

To avoid the undesirable effects generally associated with high levelsof abrasive, the amount of abrasive included in known toothpasteformulations is generally limited to between 40 and 50%. See, forexample, the Delaney et al patents mentioned above, and Crocker U.S.Pat. No. 2,128,917 which discloses incorporating sodium bicarbonatepassing a #200 mesh sieve (74 microns) in an amount of up to 50% of atoothpaste formulation.

Formulation stability is also a frequent problem with sodium bicarbonatecontaining toothpastes. Sodium bicarbonate is unstable in aqueoussolution and releases carbon dioxide gas. As a result, the pH ofbicarbonate based toothpastes increases during the requisite degassingprocedure. It is desirable that dentifrice compositions have a pH closeto the neutral range (e.g., pH of 5-9) to avoid damaging sensitive oraltissues. Moreover, in fluoride containing formulations, an increased pHmay cause reduced fluoride uptake by tooth enamel. See, for example, theaforesaid Delaney et al U.S. Pat. No. 3,943,240 (column 1, lines 32-34)and U.S. Pat. No. 3,937,803 (column 9, lines 15-21), which caution thatdegassing be discontinued before the pH of the composition increases byone pH unit, even though degassing may be incomplete.

Another problem encountered in formulating a sodium bicarbonate basedtoothpaste is that sodium bicarbonate is not always compatible withother abrasive materials in the formulation. See, for example, Delaneyet al U.S. Pat. No. 3,943,240 at column 2, lines 58-62.

Thus, it is among the objects of the present invention to provide asodium bicarbonate based toothpaste containing higher amounts ofbicarbonate than in previous formulations, which toothpaste is effectivein removing plaque and retarding stain build-up on the teeth withoutdeleterious abrasion of tooth enamel, cementum or dentin, and whichtoothpaste substantially overcomes the formulation problems previouslyencountered, such as poor dispensibility, consistency, stability, andincreased pH on degassing.

Other objects and advantages of the invention will be apparent from thefollowing description of preferred embodiments thereof.

DISCLOSURE OF THE INVENTION

In accordance with the present invention, a toothpaste is providedcomprising sodium bicarbonate as the sole abrasive material in an amountof at least about 60% by weight of the formulation, and wherein at leastabout 30% by weight of the sodium bicarbonate is of a particle size lessthan 25 microns. Toothpaste formulations prepared in accordance withthis invention provide cleaning and stain removal properties comparableto the leading commercial toothpastes. The toothpaste hereof has thefurther advantage of being low in abrasion despite its high content ofabrasive material, as well as possessing desirable consistency andtexture. Also, the sodium bicarbonate toothpaste of the invention isstable on storage, even at elevated temperatures. Unlike existing sodiumbicarbonate toothpastes, the toothpaste of this invention has virtuallyno tendency to excessively increase in pH on degassing.

It has now been found that, contrary to expectation, higher levels ofsodium bicarbonate--e.g., from about 60-75% by weight--can beincorporated in toothpastes if finer particle size baking soda is used.Toothpaste formulations including such an abrasive, i.e., a bicarbonatein which at least 30%, preferably from about 40 to 100%, of itsparticles have sizes of from about 5 to 25 microns, provide adequatestain removal without the addition of any further abrasive. Moreover,the finer particle size bicarbonate abrasives employed herein do notadversely affect slurry viscosity during toothpaste formulation. Infact, the viscosity decreases as particle size decreases. Thus, a sodiumbicarbonate based toothpaste incorporating the particular sizedbicarbonate according to this invention, exhibits both good cleaningproperties and formulating and dispensing characteristics.

A particularly significant advantage of the formulation of the inventionis the ability to provide satisfactory stain removal properties withouthaving to include a second abrasive therein. Surprisingly, the lowabrasivity generally associated with sodium bicarbonate basedtoothpastes is not increased in toothpastes formulated according to theinvention, even though stain removal properties are improved. Thus afurther, although unexpected advantage of the toothpaste of the presentinvention is that, while providing adequate stain and plaque removal, itis generally lower in abrasivity than commercial dentifrices. Lowabrasion to dental enamel and dentin is of considerable importance formaintaining and preserving the teeth.

A further, and surprising, advantage of the toothpaste of the inventionis that, unlike sodium bicarbonate toothpaste formulations previouslyreported, the pH has no tendency to rise during degassing. In fact, noincrease in pH of the present formulation is recorded, even if degassingis continued for extended periods, e.g., 1 hour. Thus, unlike thetoothpastes disclosed in the aforesaid Delaney et al patents, whereindegassing was discontinued prior to complete deaeration to avoid pHincreases of greater than one pH unit, in preparing the toothpaste ofthe present invention deaeration can proceed to completion.

The toothpaste formulation of the invention also includes at least ahumectant and a thickener. Examples of humectants include glycerol,propylene glycol, sorbitol, polyethylene glycols (generally of formulaH(OC₂ H₄)_(n) OH), and other materials known to those skilled in theart. The humectant may be present in the toothpaste in an amount of upto about 35%, preferably in an amount of about 8 to 25%, by weight ofthe toothpaste formulation. Suitable thickeners include sodiumcarboxymethylcellulose, xanthan gum, methyl cellulose, hydroxyethylcellulose, carrageen, gum karaya, gum tragacanth, gum arabic, colloidalcomplex magnesium aluminum silicates (e.g. "Veegum", manufactured byR.T. Vanderbilt Co.), and sodium alginate. The thickener is incorporatedin the toothpaste in an amount of up to about 3%, preferably within therange of about 0.3 to 1.5%, by weight of the toothpaste.

The toothpastes of the present invention preferably contain otheringredients in addition to sodium bicarbonate, a humectant, and athickening agent. The toothpaste may thus contain water in an amountnecessary to achieve formulation of the toothpaste, e.g., from about 0to 25% by weight. Additional ingredients may include surfactants,flavoring agents, sweeteners, and fluoridating agents, as recognized bythose skilled in the art.

Suitable surfactants include anionic surfactants such as the sulfates oflong chain (C₈ -C₁₈) alcohols e.g. sodium lauryl sulfate or sodiumtridecyl sulfate, the sulfates or sulfonates of monoglycerides e.g.sodium lauroyl glyceryl sulfate or sodium coconut monoglyceridesulfonate; the sulfonates of succinic esters e.g. sodium dioctylsulfosuccinate; the alkyl sulfoacetates such as sodium laurylsulfoacetate or sodium coconut sulfoacetate; the salts of sulfoaceticacid amidified with amino ethyl long chain fatty acid esters such assodium sulfocolaurate; the amides formed from higher fatty acids withshort chain amino acids such as sodium lauroyl sarcosinate or sodiummethyl lauroyl tauride and soaps such as the sodium, potassium ortriethanolamine salts of fatty acids. Similarly non-ionic surfactantsmay be used such as the ethoxylated sugar esters of the higher fattyacids for example ethoxylated sorbitan monostearate and ethoxylatedglycol monostearate. Also amphoteric surfactants such as the mono ordicarboxylated imidazoline derivatives of fatty acids such as sodiumlauryl dicarboxy imidazoline or sodium coconut dicarboxy imidazoline maybe used. Cationic surfactants may also be used in the invention. Thesematerials may impart significant antibacterial action to the product.Examples are benzyl dimethyl stearyl ammonium chloride and cetylpyridinium chloride. The surfactant(s) are present in the toothpaste inan amount of up to about 5.0%, preferably within the range of about 0.3%to 2.0%, by weight of the toothpaste.

The flavor of a sodium bicarbonate containing toothpaste is affected bythe particle size of the sodium bicarbonate. Generally, the saltiness ofthe toothpaste increases as the particle size decreases. However, theeffect of small particle size sodium bicarbonate in a toothpasteformulation is not as pronounced as in tooth powders. It is believedthat the presence of the humectant and thickening agents in thetoothpaste formulation retard bicarbonate dissolution in the mouth andthus reduce the adverse saltiness. It should, however, be understoodthat this hypothesis does not, in any way, limit the scope of thepresent invention.

Moreover, much of the saltiness can be masked by the addition ofoptional flavoring agents and/or sweeteners to the toothpasteformulation. Suitable flavoring agents include the flavoring oils, forexample, peppermint, spearmint, menthol, wintergreen, clove, cinnamon,lemon, orange, methylsalicylate, licorice, or eucalyptus. The flavoringagent may be present in the toothpaste in an amount up to about 5.0%,preferably in an amount within the range of about 0.3 to 2.0% by weightof the toothpaste. Suitable sweeteners include sodium saccharin, sodiumor calcium cyclamate, aspartame, and other sweeteners known to thoseskilled in the art. The sweetener may be present in the toothpaste in anamount of up to about 5.0%, preferably about 0.3 to 2.0%, by weight ofthe toothpaste. It should be noted that humectants, e.g. sorbitol, maysweeten the formulation to some degree. However, the amount of humectantpresent in the composition is not included in the range of sweetener setforth above.

The toothpastes of the present invention may additionally contain afluoridating agent to aid in preventing dental caries. Many fluoridatingagents suitable for use in dentrifrice compositions are known. Amongthese are sodium, potassium, lithium or ammonium fluorides, organicamine fluorides, monofluorophosphate salts such as sodium, potassium,lithium and ammonium monofluorophosphate, sodium fluorosilicate, sodiumfluorozirconate, and other materials well known to those skilled in theart. The fluoridating agents are present in an effective but non-toxicamount, e.g., in amounts of up to about 2.0%, and preferably in anamount to provide a fluoride level equivalent to about 1000 ppm offluoride ion.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred toothpaste formulations of the invention comprises about62.0 to 75.0% by weight of sodium bicarbonate, at least about 30% ofwhich has a particle size under 25 microns, desirably about 5 to 25microns. Preferably, the fine particles comprise about 40.0 to 100.0% ofthe sodium bicarbonate included in the formulation. Of the remainingsodium bicarbonate content, about 65.0-100.0% has a particle size offrom 25 to 210 microns, preferably from about 25 to 88 microns.

It is particularly preferred to incorporate the following ingredients inthe bicarbonate-containing toothpaste of the invention:

    ______________________________________                       % By Weight    ______________________________________    sodium bicarbonate   62-76    Less than 5 microns  0-5    5-25 microns          35-100    25-88 microns         0-60    humectant             8-25    (preferably glycerol or mixtures    with polyethylene glycol of    molecular weight 400 (e.g.    Carbowax 400)    thickener            0.3-1.5    (preferably sodium carboxy-    methyl cellulose)    surfactant           0.2-1.0    (preferably sodium lauryl    sulfate and/or sodium    lauroyl sarcosinate    flavoring agent      0.3-2.0    sweetener            0.3-2.0    (preferably saccharin)    fluoridating agent   0.22-0.76    (preferably sodium fluoride/    sodium monofluoro-    phosphate)    ______________________________________

The preferred toothpastes of the present invention are prepared by firstmixing the thickener with the humectant. A water solution containing thesweetener, surfactant and fluoride is added to the thickener-humectantmixture. Then, the sodium bicarbonate is stirred into the mixture.Finally, the flavor oil is added. The composition is then deaeratedunder vacuum, e.g., at about 26-30 inches of mercury, the vacuum beingreleased every few minutes to improve release of the trapped gases, andthen reapplied. The deaeration process is generally completed in about20 minutes.

The following examples illustrate particularly preferred embodiments ofthe toothpaste of the present invention. In the examples all parts andpercentages are given by weight.

EXAMPLES 1-3 TEXTURE AND DISPENSING CHARACTERISTICS OF TOOTHPASTESCONTAINING 62% SODIUM BICARBONATE

62% Sodium Bicarbonate

Examples of the sodium bicarbonate containing toothpaste of theinvention were prepared from the following formulation. The exampleswere compared with controls based on the same formulation but containingbicarbonate components having differing particle size distributions inorder to show the effect of the bicarbonate particle size distributionon the texture and dispensing pressure of the resulting product.

    ______________________________________                    Formulation I    ______________________________________    Sodium bicarbonate                      62.0    Water             18.13    Glycerine         17.1    Carboxymethylcellulose                      0.75    Sodium fluoride   0.22    Sodium lauryl sulfate                      0.3    Sodium lauroyl sarcosinate                      0.3    Flavor            0.7    Saccharin         0.5                      100.0%    ______________________________________

Dispensing pressure and texture were evaluated. Dispensing pressure wasdetermined by measuring the pressure required to eject a 26 mm strip oftoothpaste through a 7 mm orifice. Dispensing pressure of a toothpastecomposition is of concern because it is directly related to thedispensing of the paste from the tube and onto a toothbrush. Texture wasevaluated visually using the following rating system: 1--very creamysmooth; 2--creamy smooth; 3--creamy, slightly gritty; 4--dry, slightlygritty; 5--dry, gritty.

Examples 1, 2 and 3 representing variations of Formulation I within thescope of the invention, were compared with Controls A and B, which arevariations of Formulation I containing sodium bicarbonate havingdiffering particle size distributions and "Crest" toothpaste (ControlC). It should be noted that control B contains the commercial grade ofsodium bicarbonate (baking soda) available to consumers, i.e, grade 1.The results are summarized in Table I:

                                      TABLE I    __________________________________________________________________________    COMPARATIVE TEXTURE AND DISPENSING    CHARACTERISTICS OF TOOTHPASTES CONTAINING    62% SODIUM BICARBONATE HAVING VARYING    PARTICLE SIZE DISTRIBUTIONS                    CONTROL                          C     EXAMPLE                    A  B  ("Crest")*                                1  2  3    __________________________________________________________________________    More than 149 microns                    92.5                       0.5      0  0  0    89-149 microns  6.5                       19.5     0  13 0    45-88 microns   1.0                       50       15 33 0    25-44 microns   0  18       45 12 0    Less than 25 microns                    0  12       40 42 100    Initial dispensing pressure (lbs.)                    5.25                       2.37                          3.12  2.0                                   2.25                                      2.50    Dispensing pressure (lbs.), after                    8.2                       4.75                          3.50  3.1                                   3.6                                      3.0    3 weeks at 125° F.    Dispensing pressure (lbs.), after                    23.1                       6.0                          4.0   3.8                                   3.8                                      3.3    9 weeks at 125° F.    Initial texture rating                    5  4  1     1  3  1    Texture rating after                    5  4  1     4  3  2    9 weeks at 125° F.    __________________________________________________________________________     *Contains sodium fluoride in a base of sorbitol (humectant), water,     hydrated silica (abrasive), trisodium phosphate (buffer), sodium lauryl     sulfate (surfactant), flavor, titanium dioxide (to improve color, and as     second abrasive), sodium phosphate (buffer), xanthan gum (thickening     agent), Carbomer 940 (an acrylic type of polymeric thickening/emulsifying     agent), sodium saccharin (sweetener) and FD&C Blue #1 (colorant).

The above comparisons demonstrate that when the level of smallerparticle size sodium bicarbonate crystals is increased, the dispensingpressure is lower and the smoothness of the toothpaste is greater, thanwhen larger bicarbonate particles are employed in the formulation. Ascan be seen from the data presented in Table I, Examples 1, 2 and 3prepared in accordance with the present invention had low dispensingpressures which were comparable with "Crest" (Control C). Additionally,Examples 1, 2 and 3 had acceptable creamy textures.

In contrast Control A, incorporating coarse crystals of sodiumbicarbonate, had an unacceptably high dispensing pressure especially onaging. Control B, a toothpaste prepared with a quantity of fine crystalsof sodium bicarbonate, below the level of the invention, had aninitially acceptable dispensing pressure. However, on aging thedispensing pressure increased beyond an acceptable level. Both ControlsA and B had unacceptably dry textures.

EXAMPLES 4-5 TEXTURE AND DISPENSING CHARACTERISTICS OF TOOTHPASTESCONTAINING 70% SODIUM BICARBONATE

Further toothpastes were prepared, and dispensing pressure and texturecomparisons performed, employing compositions prepared from thefollowing formulations containing 75% (Example 4) and 70% (Example 5)sodium bicarbonate, respectively: the results, which are set forth inTable II, show that even at sodium bicarbonate levels of 70% and above,low dispensing pressures and acceptable consistencies are obtained.

                  TABLE II    ______________________________________    COMPARATIVE TEXTURE AND DISPENSING    CHARACTERISTICS OF TOOTHPASTES CONTAINING    70% AND 75% SODIUM BICARBONATE HAVING    VARYING PARTICLE SIZE DISTRIBUTIONS                         EXAMPLE                         4    5    ______________________________________    Sodium bicarbonate     75     70    Water                  13.08  18.08    Glycerin               9.38   9.38    Xanthan gum            0.25   0.25    Carboxymethylcellulose 0.25   0.25    Sodium Fluoride        0.24   0.24    Sodium Lauryl Sulfate  0.3    0.3    Sodium Lauroyl Sarcosinate                           0.3    0.3    Flavor                 0.7    0.7    Saccharin              0.5    0.5    Particle size of bicarbonate used    more than 149 microns  0      0    89-149 microns         12     11    45-88 microns          30     29    25-44 microns          11     10    Less than 25 microns   47     50    Initial dispensing pressure                           NT*    4.2    Dispensing pressure (lbs.) after                           4.8    5.7    1 week at 125° F.    Dispensing pressure (lbs.) after                           NT*    3.8    3 weeks at 125° F.    ______________________________________     *NT -- Not tested

EXAMPLES 6-9 STAIN REMOVAL AND ABRASIVE PROPERTIES OF TOOTHPASTESCONTAINING 65% SODIUM BICARBONATE

Tests were run to illustrate the stain removal and abrasion propertiesof sodium bicarbonate based toothpastes. Examples 6 through 9 andControls D, E and F incorporated the ingredients specified inFormulation II below. Examples 6 through 9 contain varying bicarbonateparticle size distributions in accordance with the invention.

The stain removal properties of the various toothpaste compositions wereevaluated using a simulated stain removal test. Ceramic tiles werestained with concentrated tea solution, and the stain was fixed bydipping the tiles in ferrous sulfate. A slurry of test product (2 parts)and water (1 part) was placed on each test tile and the tile was brushedin a Gardner straight line washability machine for 50 cycles. The tileswere then rinsed and dried. Stain removal was determined by comparingthe reflectance before and after brushing.

Examples 6 through 9 were compared with Controls D, E and F, and with"Crest" (Control C) for stain removal efficiency. The results are setforth below.

    ______________________________________                     Formulation II    ______________________________________    Sodium Bicarbonate 65    Water              16.63    Glycerin           15.60    Carboxymethylcellulose                       0.75    Sodium Fluoride    0.22    Sodium Lauryl Sulfate                       0.30    Sodium Lauroyl Sarcosinate                       0.30    Flavor             0.70    Saccharin          0.50    ______________________________________

                                      TABLE III    __________________________________________________________________________    COMPARATIVE STAIN REMOVAL AND ABRASIVE PROPERTIES OF    TOOTHPASTES CONTAINING 65% SODIUM BICARBONATE    HAVING VARYING PARTICLE SIZE DISTRIBUTIONS                CONTROL       EXAMPLE                D   E  F   C  6  7  8  9    __________________________________________________________________________    More than 149 microns                 0.5                     0  0.5    0 0   0 0    89-149 microns                19.5                    11 16.5    0 6  14 0    45-88 microns                50  35 43     15 16 34 0    25-44 microns                18  30 15     45 6  12 0    Less than 25 microns                12  24 25     40 72 40 100    Increase in Reflectance                 13.2*                    19.8*                        22.7*                           31.0°                              27.3°                                 27.6°                                    28.0°                                       31.0°    (Higher value equals    better stain removal    __________________________________________________________________________       "Crest"-     *Worse performance than Control C, and Examples 6-9 (>95% Confidence     Level)     °Not significantly different than Control C.

The stain removal comparisons demonstrate that stain removal propertiesgenerally increase with an increase in the proportion of the sodiumbicarbonate particles having sizes less than 25 microns. Controls D, Eand F, all containing 25% or less sodium bicarbonate particles sizedbelow 25 microns, performed significantly poorer in the stain removaltests than Examples 6-9, and Control C.

EXAMPLES 10-14 STAIN REMOVAL PROPERTIES OF TOOTHPASTES CONTAINING 62%SODIUM BICARBONATE AND INCORPORATING VARYING WATER TO HUMECTANT RATIOS

Another stain removal comparison was performed to determine whethervariations in the water to humectant ratio would affect the stainremoval properties of toothpastes formulated in accordance with theinvention. Examples 10 through 14 and Controls G, H and I incorporatedthe composition of Formulation III, set forth below. Stain removal wasevaluated as described in Examples 6-9, above.

    ______________________________________                     Formulation III    ______________________________________    Sodium bicarbonate 62.0    Water + Glycerin*  35.23    Carboxymethylcellulose                       0.75    Sodium fluoride    0.22    Sodium lauryl Sulfate                       0.3    Sodium lauroyl Sarcosinate                       0.3    Flavor             0.70    Saccharin          0.50                       100.00    ______________________________________     *Ratios as set forth in Table IV.

                                      TABLE IV    __________________________________________________________________________    COMPARATIVE STAIN REMOVAL PROPERTIES OF TOOTHPASTES    CONTAINING 62% SODIUM BICARBONATE HAVING DIFFERENT    PARTICLE SIZE DISTRIBUTIONS AND VARYING WATER TO    HUMECTANT RATIOS            CONTROL       EXAMPLE            G  H   I   C  10  11  12  13  14    __________________________________________________________________________    More than            92.5                0.5                    0.5    0  0    0   0  0    149 microns    89-149 microns            6.5               19.5                   19.5   13  0   13  13  0    45-88 microns            1.0               50  50     33  0   33  33  0    25-44 microns            0  18  18     12  0   12  12  0    Less than            0  12  12     42  100 42  42  100    25 microns    Water/  1.1/1               1.3/1                   0.6/1.0                          1.3/1.0                              0.6/1.0                                  1.1/1.1                                      0.6/1.0                                          1.3/1.0    Glycerin Ratio    Increase in             5.6*                14.7*                    14.9*                       22.4                          18.4°                              19.0°                                  20.3°                                      21.7°                                          23.0°    Reflectance    __________________________________________________________________________       "Crest"-     *Significantly worse performance than Control C and Examples 12-14 (>95%     Confidence Level)     °Not significantly different than Control C.

The above comparisons generally confirm that increasing the quantity ofsodium bicarbonate particles under 25 microns in the compositionimproves stain removal. Thus, it is possible to formulate toothpasteshaving sodium bicarbonate as the sole abrasive, without sacrificing thestain removal achieved by commercially available products such as"Crest". Additionally, Table IV demonstrates that varying the water tohumectant ratio does not significantly affect stain removal. Examples10-14, prepared in accordance with the invention, have stain removalproperties equivalent to that of the "Crest" control.

EXAMPLES 15-16 STAIN REMOVAL PROPERTIES OF TOOTHPASTES CONTAININGVARYING PROPORTIONS OF SODIUM BICARBONATE

Comparisons of stain removal properties of toothpastes containingvarious total amounts of sodium bicarbonate show that if sodiumbicarbonate is used as the sole abrasive high levels (65%--Example 15;or 75%--Example 16) are required to obtain the desired cleaningcapacity.

Stain removal comparisons were performed in the manner previouslydescribed. The results, which are summarized in Table V, show that stainremoval generally increases with a corresponding increase in the amountof sodium bicarbonate, provided the requisite level of fine particles ofbaking soda is maintained. As shown, at least 60% sodium bicarbonate isnecessary to achieve stain removal equivalent to the commercialdentifrice.

Moreover, and contrary to expectation, solely using sodium bicarbonateparticles under 25 microns in size, but at a total percentage of lessthan 60%, does not significantly improve stain removal properties. Thus,a sodium bicarbonate based toothpaste containing baking soda as the soleabrasive only achieves the stain removal performance of a commercialdentifrice, if at least 60% sodium bicarbonate, with greater than 30% ofthe bicarbonate particles being smaller than 25 microns is included inthe formulation.

                  TABLE V    ______________________________________    COMPARATIVE STAIN REMOVAL CHARACTERISTICS    OF TOOTHPASTES CONTAINING VARYING TOTAL    AMOUNTS OF SODIUM BICARBONATE    ______________________________________                   CONTROL     EXAMPLE                     J      K      L     15   16    ______________________________________    Sodium Bicarbonate                     40     40     50    65   75    Water + Glycerin (Ratio 1:1) 56.78                     56.78  46.98  32.28 22.48    Carboxymethylcellulose                     1.20   1.20   1.00  0.70 0.50    Sodium Fluoride  0.22   0.22   0.22  0.22 0.22    Sodium Lauryl Sulfate                     0.30   0.30   0.30  0.30 0.30    Sodium Lauroyl Sarcosinate                     0.30   0.30   0.30  0.30 0.30    Flavor           0.70   0.70   0.70  0.70 0.70    Saccharin        0.50   0.50   0.50  0.50 0.50    ______________________________________                   PARTICLE SIZE DISTRIBUTION                   OF BICARBONATES USED    ______________________________________    More than 149 microns                     0      0      0     0    0    89-149 microns   0      14     14    14   14    45-88 microns    0      34     34    34   34    24-44 microns    0      12     12    12   12    Less than 25 microns                     100    40     40    40   40    ______________________________________             STAIN REMOVAL CHARACTERISTICS                                  Control C               J      K      L    ("Crest")                                          15   16    ______________________________________    Increase in Re-               15.4*  13.4*  16.8*                                  23.0    24.4°                                               29.2**    flectance    ______________________________________      *Significantly poorer than Examples 15 and 16, and Control C. (>92%     Confidence Level)     °Same as Control C ("Crest")     **Significantly better than Control C ("Crest") (>95% Confidence Level)

EXAMPLES 17-18 ABRASIVE CHARACTERISTICS OF TOOTHPASTES CONTAINING 62%SODIUM BICARBONATE, As Compared With Commercial Toothpaste Formulations

The abrasivity of Examples 17 and 18 was compared with the abrasivecharacteristics of Controls M, N and O. Examples 17 and 18, and ControlM, were prepared from Formulation I (set forth above), with Examples 17and 18 containing a sodium bicarbonate particle size distributionaccording to the present invention. Controls C, N and O were commercialtoothpastes ("Crest", "Aim" and "Colgate"); the latter two formulationscontain calcium pyrophosphate as the abrasive therein.

In the abrasion studies, the test toothpastes were compared for relativeenamel and dentin abrasivity using the method of J. J. Hefferren ("ALaboratory Method for Assessment of Dentifrice Abrasivity,"J.Dent.Research 55, 563-573, 1976). Relative enamel abrasivity wasdetermined by abrading the crowns of freshly extracted irradiated humanteeth, using slurries of the test compositions. The enamel removed wasquantitated by the level of radioactive phosphorus abraded into theslurry. Similarly, relative dentin abrasivity was measured by abradingthe roots of freshly extracted irradiated teeth, and determining theamount of radioactive dentin removed. The results were also comparedwith that of a calcium pyrophosphate control.

Slurries of Examples 17 and 18 and Control M were prepared using 25grams of paste in 50 ml. water. A 10 g control slurry of calciumpyrophosphate in 50 ml. of 0.5% aqueous carboxymethylcellulose was givenan arbitrary abrasivity value of 100.

The results demonstrate that there is no significant difference indentin or enamel abrasivity between the test toothpastes containingsodium bicarbonate levels in accordance with the invention (Examples 17and 18) and that toothpaste (Control M) formulated with less than 30% ofthe baking soda particles smaller than 25 microns. Also, as can be seen,the toothpaste compositions of the invention are significantly lower indentin abrasivity than the commercial products (Controls C, N and O).

                                      TABLE VI    __________________________________________________________________________    COMPARATIVE ABRASIVE CHARACTERISTICS OF TOOTHPASTES    CONTAINING SODIUM BICARBONATES HAVING VARYING    PARTICLE SIZE DISTRIBUTION, WITH COMMERCIAL CONTROL    TOOTHPASTE FORMULATIONS                CONTROL        EXAMPLE                C        N O   17                ("Crest")                     M   ("Aim").sup.1                               ("Colgate").sup.2                                      18    __________________________________________________________________________    More than 149 microns                      0.5       0      0    89-149 microns   19.5       0     13    45-88 microns    50        15     33    25-44 microns    18        45     12    Less than 25 microns                     12        40     42    Relative dentin                71    44*                         64                           63   43*    46*    abrasivity    Relative enamel                21     9**                         10                            12**                                10**   11**    abrasivity    __________________________________________________________________________     *Lower abrasivity than controls C, N and O. (>95% Confidence Level)     **Lower abrasivity than controls C and N. (>95% Confidence Level)     .sup.1 Aim contains sodium monofluorophosphate in a base of sorbitol,     hydrated silica, PEG 32, water, sodium lauryl sulfate, SD alcohol 38B,     flavor, cellulose gum, sodium saccharin, sodium benzoate, FD&C Blue #1,     D&C Yellow #10.     .sup.2 Colgate contains sodium monofluorophosphate in a base of dicalcium     phosphate dihydrate, water, glycerin, sodium lauryl sulfate, cellulose     gum, flavor, sodium benzoate, tetrosodium pyrophosphate, sodium saccharin

EXAMPLES 19-20 ABRASIVE CHARACTERISTICS OF TOOTHPASTES CONTAINING 40%AND 100% SODIUM BICARBONATE AS COMPARED WITH "CREST"

Two additional sodium bicarbonate based toothpastes prepared inaccordance with the present invention were compared with "Crest", forrelative abrasivity to enamel and dentin. These results show that asodium bicarbonate toothpaste wherein all the sodium bicarbonateparticles are smaller than 25 microns, has significantly lowerabrasivity than "Crest".

    ______________________________________                     Example 19                             Example 20    ______________________________________    Sodium bicarbonate 62        65    Water              18.13     16.63    Glycerin           17.1      15.6    Carboxymethylcellulose                       0.75      0.75    Sodium Fluoride    0.22      0.22    Sodium Lauryl Sulfate                       0.3       0.3    Sodium Lauroyl Sarcosinate                       0.3       0.3    Flavor             0.7       0.7    Saccharin          0.5       0.5    ______________________________________

                  TABLE VII    ______________________________________    ABRASIVE CHARACTERISTICS OF TOOTHPASTES    CONTAINING SODIUM BICARBONATES HAVING    VARYING PARTICLE SIZE DISTRIBUTIONS,    AS COMPARED WITH "CREST"                 CONTROL                 C          EXAMPLE                 ("Crest")  19      20    ______________________________________    More than 149 microns       0        0    89-149 microns              0       14    45-88 microns               0       34    22-24 microns               0       12    Less than 25 microns        100     40    Relative dentin abrasivity                   90           47*      47*    Relative enamel abrasivity                   24           18      21    ______________________________________     *Lower abrasivity than control (>95% Confidence Level)

EXAMPLES 21-23 DEGASSING CHARACTERISTICS OF TOOTHPASTES CONTAININGSODIUM BICARBONATES HAVING VARYING PARTICLE SIZE DISTRIBUTIONS

As previously discussed, the toothpastes of this invention can betotally degassed without significant increase in pH. Tests were runcomparing the pH, before and after degassing, of three toothpastecompositions of the invention. The results, which are summarized inTable VIII below, show that there is no significant change in pH afterdegassing has been completed.

                  TABLE VIII    ______________________________________    COMPARISON OF pH BEFORE AND AFTER    DEGASSING OF FORMULATIONS CONTAINING    SODIUM BICARBONATES HAVING THE PARTICLE SIZE    DISTRIBUTION OF THE INVENTION                    EXAMPLE                    21      22      23    ______________________________________    Sodium Bicarbonate                      62        62      62    Water             19.91     18.13   16.78    Glycerin          15.32     17.1    18.54    Carboxymethylcellulose                      0.75      0.75    0.75    Sodium Fluoride   0.22      0.22    0.22    Sodium Lauryl Sulfate                      0.3       0.3     0.3    Sodium Lauroyl Sarcosinate                      0.3       0.3     0.3    Flavor            0.7       0.7     0.7    Saccharin         0.5       0.5     0.5    Particle Size of bicarbonate used    More than 149 microns                      0         0       0    89-149 microns    13        0       13    45-88 microns     33        0       33    25-44 microns     12        0       12    Less than 25 microns                      42        100     42    pH before degassing                      9.15      9.3     9.0    pH after degassing                      8.9       8.9     9.1    ______________________________________

It will be understood that the preferred toothpaste compositions of theinvention described herein are illustrative only, and should not beconstrued as limiting the present invention.

What is claimed is:
 1. In a toothpaste containing an abrasive, ahumectant and a thickening agent, the improvement comprising sodiumbicarbonate as the sole abrasive, the sodium bicarbonate beingincorporated in the toothpaste in an amount of at least 60% by weight,and at least 30% by weight of the sodium bicarbonate having a particlesize of less than 25 microns.
 2. The toothpaste according to claim 1,wherein the humectant is selected from the group consisting of glycerol,propylene glycol, sorbitol and polyethylene glycols.
 3. The toothpasteaccording to claim 1, wherein the thickening agent is selected from thegroup consisting of sodium carboxymethylcellulose, xanthan gum, methylcellulose, hydroxyethyl cellulose, carrageen, gum karaya, gumtragacanth, gum arabic, and sodium alginate.
 4. The toothpaste accordingto claim 1 further comprising a surfactant.
 5. The toothpaste accordingto claim 1, further comprising from 0.3 to 5.0% by weight of a flavoringagent.
 6. The toothpaste according to claim 1, further comprising from0.3 to 5.0% by weight of a non-humectant sweetener.
 7. A sodiumbicarbonate based toothpaste comprising from 60 to 75% by weight sodiumbicarbonate, at least 30% of said sodium bicarbonate having a particlesize of less than 25 microns; from 5 to 25% by weight of a humectant;from 0.3 to 3.0% by weight of a thickener; from 0.3 to 5.0% by weight ofa surfactant; from 0.3 to 5.0% by weight of a flavoring agent; and from0.3 to 5.0% by weight of a sweetener.
 8. The toothpaste of claim 8,wherein from 25% to 100% of the sodium bicarbonate has a particle sizeof from 5 to 25 microns, and from 60 to 100% of the sodium bicarbonatehas a particle size of from 25 to 210 microns.
 9. The toothpaste ofclaim 7, wherein the humectant is selected from the group consisting ofglycerol, propylene glycol, sorbitol, and polyethylene glycols.
 10. Thetoothpaste of claim 7, wherein the thickener is selected from the groupconsisting of sodium carboxymethylcellulose, xanthan gum, methylcellulose, hydroxyethyl cellulose, carrageen, gum karaya, gumtragacanth, gum arabic, and sodium alginate.